It’s not that Joe Biden does anything. It’s that Joe Public scorns them. Moderate republicans would become moderates, and moderates would become moderate liberals, and moderate liberals would become strong liberals - at least for the next few years until the gut reaction wore off. And with a liberal-by-the-numbers congress already in place, a lot could happen in those few years.
9-11 was an example of this sort of situation.
Moderation will become a crime against the state.
There’ll be Caucasian rioting in the streets, which will mostly be made up of recipe exchanges. But the recipes won’t be very good and they will all be a kind of hotdish!
I don’t think the political upheaval resulting from an assassination would undo the country, but the economic impact might.
Global reactions would come into play and if the President were assassinated by Al-Qaeda, for example, I think our resources are stretched far too thin to make any kind of meaningful response.